The present invention relates to a steel laminate gasket of a very thin type with a graphite sheet.
A conventional steel laminate gasket is constructed by laminating several plates, and is provided with a complicated sealing portion around a hole to be sealed. Consequently, it is difficult to manufacture a steel laminate gasket with light weight. Also, productivity of a steel laminate gasket is poor. As a result, a steel laminate gasket is expensive more than other gaskets.
In a small engine, a gasket must be light weight and manufactured at a low cost. However, a conventional steel laminate gasket is heavy and expensive. Therefore, a conventional steel laminate gasket is not usually used for a small size engine.
On the other hand, when engine parts to which a gasket is attached, such as a cylinder head and a cylinder block, are manufactured, small projections, dents or scratches are formed on gasket attaching portions by cutter trace.
In order to securely seal between the engine parts by a gasket, it is necessary to fill the dents or scratches. Otherwise, fluid may leak through the dents or scratches especially when high pressure is applied to the gasket.
Conventionally, a coating is formed on an outer surface of the gasket in order to fill the dents or scratches. In case a soft coating, such as gum or synthetic resin, is applied on the gasket, the coating must be thin. Generally, the soft coating can be applied onto the gasket to fill the dents or scratches under 8-10 micrometers on the engine parts.
In case the dents or scratches are large or deep more than 8-10 micrometers, if a large amount of soft coating is applied onto the gasket, the soft coating causes flow in use, which reduces surface pressure on the gasket to cause leakage. Therefore, a large amount of a soft coating can not be applied onto the gasket.
In case the dents or scratches are deep more than 8-10 micrometers, therefore, the surface of the engine part are ground additionally for reducing the dents or scratches under 8-10 micrometers.
In U.S. Pat No. 3,841,289, graphite sheets are laminated on a metal plate, wherein when a gasket is tightened, the graphite sheets are compressed further to withstand variable cylinder pressure and temperature.
However, even if the graphite sheets are compressed at maximum density, if high heat and pressure are applied in use, the graphite sheets may partly flow to reduce surface pressure thereat.
Accordingly, one object of the present invention is to provide a steel laminate gasket, which is light in weight and simple in structure.
Another object of the invention is to provide a steel laminate gasket as stated above, which includes a material for filling dents or scratches on engine parts without causing flow in use.
Further objects and advantages of the invention will be apparent from the following description of the invention.